DO NOT click on the Amendment option ... when you log in you should be given the option to continue the return.  If you do not see that then scroll down and click on ADD A STATE to open the account.  

NO, do not click on Amend, or you'll have problems.

If TurboTax thinks you might be finished, the return interview may be closed.  If it is, here's how to open it back up to resume:

• Log in and at the Tax Home or in the section "Your Tax Returns & Documents" for 2020, look for a link "Add a State."
• Click on "Add a State."  (you don't really add one.  That's just to open your return back up.)